Fix shell search suggestion pick after dismissing OSK with B

[CyberoniOntoni]

What & why

When searching from the shell AutoSuggestBox on Xbox, pressing B to dismiss the on-screen keyboard spuriously fired QuerySubmitted / SuggestionChosen with the first suggestion, immediately navigating to that title instead of letting the user browse the list with the d-pad.

This change suppresses those dismiss events, routes deliberate picks only through SuggestionChosen (A on a highlighted row), keeps the search box focusable while suggestions are open, and sets UpdateTextOnSelect="False" so partial query text is preserved.

Stacked on dfederm#98 — merge after dfederm#98 (shell search + Xbox focus) lands.

Fixes #

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Build / tooling
• Docs

Checklist

• Single-purpose: this PR makes one logical change and does not club together unrelated changes.
• Builds clean: msbuild JellyBox.sln -t:Build -p:Configuration=Debug -p:Platform=x64 succeeds with 0 warnings and 0 errors (verified Release x64 locally via MSBuild).
• UI/UX changes include screenshots or a short screen recording (focus and playback behavior can't be reviewed from the diff alone).
• Manual testing is described below — including the platform tested on (real Xbox strongly preferred, Windows acceptable) — for any UI, playback, or controller change.
• Linked the related issue above (if one exists).

Manual test notes

Windows desktop (Release x64 build, 0 warnings/errors). Xbox verification still needed — intended flow:

1. Focus shell search, type a partial movie/TV title until suggestions appear.
2. Press B to dismiss the OSK — suggestions stay visible; app does not navigate.
3. Use d-pad to highlight a suggestion, press A — selected item details opens.
4. Type a query and submit with Enter (no suggestion pick) — full Search results page opens.

Screenshots / recording

Not yet captured — Xbox screen recording to be added after device verification.

Out of scope / follow-ups

• Shell search bar, suggestion API, and focus coordinator work remain in Fix Xbox shell focus, search, and library filter navigation dfederm/JellyBox#98.
• Xbox device confirmation of the full flow above.

[CyberoniOntoni]

Superseded by upstream PR dfederm#101.